1. Field of the Invention
The present invention relates to a method for driving a servo-motor, and more particularly to a new improvement for detecting power voltage without using a current feedback loop, comprising a current sensor and an A/D converter, which is conventionally used for motor current detection, and controlling current using this detected value, thereby improving control properties and lowering cost.
2. Description of the Related Art
FIG. 1 shows a conventional method of this type which has generally been used as a method for driving a servo-motor.
That is, a current command Icmd is input to a calculator 1. The output 1a of the calculator 1 is sent via a proportional and/or integral controller 2 and is input as a voltage command 2a to a power converter 3, comprising a known power element configuration. The power converter 3 supplies a three-phase drive current Iu, Iv, Iw to a servo-motor 4. A current sensor 5 detects one part of the three-phase drive current Iu, Iv, Iw, and the detected current value Ivcc is input to the calculator 1 via an A/D converter 6, thereby forming a current feedback control.
Since the conventional servo-motor driving method has the configuration described above, it has problems such as the following.
That is, a current sensor and an expensive A/D converter are required in order to form the current feedback system, constituting a considerable obstacle to lowering the cost of the control system.